Thanks for your response. There is no referrer link listed for these errors. Also, the person who has been in charge of the blog says we’ve always used URLs that had the date directories ahead of the title directories (“/2016/09/14/my-post”, not “/my-post/2016/09/14”).
Here’s an example of the redirect we’re doing. This would be the .htaccess file in the root of the old domain. I’m still learning about building proper 301 redirects. Maybe you can spot an issue here:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
Redirectmatch 301 “^/(.*)” “https://www.example.com/blog/$1”
</IfModule>